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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
10		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
…		…
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head1 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head1 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	96	=head1 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	102	to the C<double> type in C, and when you need to do any calculations on
		103	it, you should treat it as such.
		104
		105	=head1 GLOBAL FUNCTIONS
		106
		107	These functions can be called anytime, even before initialising the
		108	library in any way.
51		109
52	=over 4	110	=over 4
53		111
54	=item ev_tstamp ev_time ()	112	=item ev_tstamp ev_time ()
55		113
56	Returns the current time as libev would use it.	114	Returns the current time as libev would use it. Please note that the
		115	C<ev_now> function is usually faster and also often returns the timestamp
		116	you actually want to know.
57		117
58	=item int ev_version_major ()	118	=item int ev_version_major ()
59		119
60	=item int ev_version_minor ()	120	=item int ev_version_minor ()
61		121
62	You can find out the major and minor version numbers of the library	122	You can find out the major and minor ABI version numbers of the library
63	you linked against by calling the functions C<ev_version_major> and	123	you linked against by calling the functions C<ev_version_major> and
64	C<ev_version_minor>. If you want, you can compare against the global	124	C<ev_version_minor>. If you want, you can compare against the global
65	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66	version of the library your program was compiled against.	126	version of the library your program was compiled against.
67		127
		128	These version numbers refer to the ABI version of the library, not the
		129	release version.
		130
68	Usually, it's a good idea to terminate if the major versions mismatch,	131	Usually, it's a good idea to terminate if the major versions mismatch,
69	as this indicates an incompatible change. Minor versions are usually	132	as this indicates an incompatible change. Minor versions are usually
70	compatible to older versions, so a larger minor version alone is usually	133	compatible to older versions, so a larger minor version alone is usually
71	not a problem.	134	not a problem.
72		135
		136	Example: Make sure we haven't accidentally been linked against the wrong
		137	version.
		138
		139	assert (("libev version mismatch",
		140	ev_version_major () == EV_VERSION_MAJOR
		141	&& ev_version_minor () >= EV_VERSION_MINOR));
		142
		143	=item unsigned int ev_supported_backends ()
		144
		145	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		146	value) compiled into this binary of libev (independent of their
		147	availability on the system you are running on). See C<ev_default_loop> for
		148	a description of the set values.
		149
		150	Example: make sure we have the epoll method, because yeah this is cool and
		151	a must have and can we have a torrent of it please!!!11
		152
		153	assert (("sorry, no epoll, no sex",
		154	ev_supported_backends () & EVBACKEND_EPOLL));
		155
		156	=item unsigned int ev_recommended_backends ()
		157
		158	Return the set of all backends compiled into this binary of libev and also
		159	recommended for this platform. This set is often smaller than the one
		160	returned by C<ev_supported_backends>, as for example kqueue is broken on
		161	most BSDs and will not be autodetected unless you explicitly request it
		162	(assuming you know what you are doing). This is the set of backends that
		163	libev will probe for if you specify no backends explicitly.
		164
		165	=item unsigned int ev_embeddable_backends ()
		166
		167	Returns the set of backends that are embeddable in other event loops. This
		168	is the theoretical, all-platform, value. To find which backends
		169	might be supported on the current system, you would need to look at
		170	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		171	recommended ones.
		172
		173	See the description of C<ev_embed> watchers for more info.
		174
73	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	175	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
74		176
75	Sets the allocation function to use (the prototype is similar to the	177	Sets the allocation function to use (the prototype is similar - the
76	realloc C function, the semantics are identical). It is used to allocate	178	semantics is identical - to the realloc C function). It is used to
77	and free memory (no surprises here). If it returns zero when memory	179	allocate and free memory (no surprises here). If it returns zero when
78	needs to be allocated, the library might abort or take some potentially	180	memory needs to be allocated, the library might abort or take some
79	destructive action. The default is your system realloc function.	181	potentially destructive action. The default is your system realloc
		182	function.
80		183
81	You could override this function in high-availability programs to, say,	184	You could override this function in high-availability programs to, say,
82	free some memory if it cannot allocate memory, to use a special allocator,	185	free some memory if it cannot allocate memory, to use a special allocator,
83	or even to sleep a while and retry until some memory is available.	186	or even to sleep a while and retry until some memory is available.
		187
		188	Example: Replace the libev allocator with one that waits a bit and then
		189	retries).
		190
		191	static void *
		192	persistent_realloc (void *ptr, size_t size)
		193	{
		194	for (;;)
		195	{
		196	void *newptr = realloc (ptr, size);
		197
		198	if (newptr)
		199	return newptr;
		200
		201	sleep (60);
		202	}
		203	}
		204
		205	...
		206	ev_set_allocator (persistent_realloc);
84		207
85	=item ev_set_syserr_cb (void (*cb)(const char *msg));	208	=item ev_set_syserr_cb (void (*cb)(const char *msg));
86		209
87	Set the callback function to call on a retryable syscall error (such	210	Set the callback function to call on a retryable syscall error (such
88	as failed select, poll, epoll_wait). The message is a printable string	211	as failed select, poll, epoll_wait). The message is a printable string
…		…
90	callback is set, then libev will expect it to remedy the sitution, no	213	callback is set, then libev will expect it to remedy the sitution, no
91	matter what, when it returns. That is, libev will generally retry the	214	matter what, when it returns. That is, libev will generally retry the
92	requested operation, or, if the condition doesn't go away, do bad stuff	215	requested operation, or, if the condition doesn't go away, do bad stuff
93	(such as abort).	216	(such as abort).
94		217
		218	Example: This is basically the same thing that libev does internally, too.
		219
		220	static void
		221	fatal_error (const char *msg)
		222	{
		223	perror (msg);
		224	abort ();
		225	}
		226
		227	...
		228	ev_set_syserr_cb (fatal_error);
		229
95	=back	230	=back
96		231
97	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	232	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
98		233
99	An event loop is described by a C<struct ev_loop *>. The library knows two	234	An event loop is described by a C<struct ev_loop *>. The library knows two
100	types of such loops, the I<default> loop, which supports signals and child	235	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	236	events, and dynamically created loops which do not.
102		237
103	If you use threads, a common model is to run the default event loop	238	If you use threads, a common model is to run the default event loop
104	in your main thread (or in a separate thrad) and for each thread you	239	in your main thread (or in a separate thread) and for each thread you
105	create, you also create another event loop. Libev itself does no locking	240	create, you also create another event loop. Libev itself does no locking
106	whatsoever, so if you mix calls to the same event loop in different	241	whatsoever, so if you mix calls to the same event loop in different
107	threads, make sure you lock (this is usually a bad idea, though, even if	242	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because it's hideous and inefficient).	243	done correctly, because it's hideous and inefficient).
109		244
…		…
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	247	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		248
114	This will initialise the default event loop if it hasn't been initialised	249	This will initialise the default event loop if it hasn't been initialised
115	yet and return it. If the default loop could not be initialised, returns	250	yet and return it. If the default loop could not be initialised, returns
116	false. If it already was initialised it simply returns it (and ignores the	251	false. If it already was initialised it simply returns it (and ignores the
117	flags).	252	flags. If that is troubling you, check C<ev_backend ()> afterwards).
118		253
119	If you don't know what event loop to use, use the one returned from this	254	If you don't know what event loop to use, use the one returned from this
120	function.	255	function.
121		256
122	The flags argument can be used to specify special behaviour or specific	257	The flags argument can be used to specify special behaviour or specific
123	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).	258	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
124		259
125	It supports the following flags:	260	The following flags are supported:
126		261
127	=over 4	262	=over 4
128		263
129	=item C<EVFLAG_AUTO>	264	=item C<EVFLAG_AUTO>
130		265
…		…
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	273	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	274	override the flags completely if it is found in the environment. This is
140	useful to try out specific backends to test their performance, or to work	275	useful to try out specific backends to test their performance, or to work
141	around bugs.	276	around bugs.
142		277
		278	=item C<EVFLAG_FORKCHECK>
		279
		280	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		281	a fork, you can also make libev check for a fork in each iteration by
		282	enabling this flag.
		283
		284	This works by calling C<getpid ()> on every iteration of the loop,
		285	and thus this might slow down your event loop if you do a lot of loop
		286	iterations and little real work, but is usually not noticeable (on my
		287	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		288	without a syscall and thus I<very> fast, but my Linux system also has
		289	C<pthread_atfork> which is even faster).
		290
		291	The big advantage of this flag is that you can forget about fork (and
		292	forget about forgetting to tell libev about forking) when you use this
		293	flag.
		294
		295	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		296	environment variable.
		297
143	=item C<EVMETHOD_SELECT> (portable select backend)	298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		299
		300	This is your standard select(2) backend. Not I<completely> standard, as
		301	libev tries to roll its own fd_set with no limits on the number of fds,
		302	but if that fails, expect a fairly low limit on the number of fds when
		303	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		304	the fastest backend for a low number of fds.
		305
145	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	306	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
146		307
147	=item C<EVMETHOD_EPOLL> (linux only)	308	And this is your standard poll(2) backend. It's more complicated than
		309	select, but handles sparse fds better and has no artificial limit on the
		310	number of fds you can use (except it will slow down considerably with a
		311	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
148		312
149	=item C<EVMETHOD_KQUEUE> (some bsds only)	313	=item C<EVBACKEND_EPOLL> (value 4, Linux)
150		314
151	=item C<EVMETHOD_DEVPOLL> (solaris 8 only)	315	For few fds, this backend is a bit little slower than poll and select,
		316	but it scales phenomenally better. While poll and select usually scale like
		317	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		318	either O(1) or O(active_fds).
152		319
153	=item C<EVMETHOD_PORT> (solaris 10 only)	320	While stopping and starting an I/O watcher in the same iteration will
		321	result in some caching, there is still a syscall per such incident
		322	(because the fd could point to a different file description now), so its
		323	best to avoid that. Also, dup()ed file descriptors might not work very
		324	well if you register events for both fds.
		325
		326	Please note that epoll sometimes generates spurious notifications, so you
		327	need to use non-blocking I/O or other means to avoid blocking when no data
		328	(or space) is available.
		329
		330	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		331
		332	Kqueue deserves special mention, as at the time of this writing, it
		333	was broken on all BSDs except NetBSD (usually it doesn't work with
		334	anything but sockets and pipes, except on Darwin, where of course its
		335	completely useless). For this reason its not being "autodetected"
		336	unless you explicitly specify it explicitly in the flags (i.e. using
		337	C<EVBACKEND_KQUEUE>).
		338
		339	It scales in the same way as the epoll backend, but the interface to the
		340	kernel is more efficient (which says nothing about its actual speed, of
		341	course). While starting and stopping an I/O watcher does not cause an
		342	extra syscall as with epoll, it still adds up to four event changes per
		343	incident, so its best to avoid that.
		344
		345	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		346
		347	This is not implemented yet (and might never be).
		348
		349	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		350
		351	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		352	it's really slow, but it still scales very well (O(active_fds)).
		353
		354	Please note that solaris ports can result in a lot of spurious
		355	notifications, so you need to use non-blocking I/O or other means to avoid
		356	blocking when no data (or space) is available.
		357
		358	=item C<EVBACKEND_ALL>
		359
		360	Try all backends (even potentially broken ones that wouldn't be tried
		361	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		362	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		363
		364	=back
154		365
155	If one or more of these are ored into the flags value, then only these	366	If one or more of these are ored into the flags value, then only these
156	backends will be tried (in the reverse order as given here). If one are	367	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	368	specified, most compiled-in backend will be tried, usually in reverse
		369	order of their flag values :)
158		370
159	=back	371	The most typical usage is like this:
		372
		373	if (!ev_default_loop (0))
		374	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		375
		376	Restrict libev to the select and poll backends, and do not allow
		377	environment settings to be taken into account:
		378
		379	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		380
		381	Use whatever libev has to offer, but make sure that kqueue is used if
		382	available (warning, breaks stuff, best use only with your own private
		383	event loop and only if you know the OS supports your types of fds):
		384
		385	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
160		386
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	387	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		388
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	389	Similar to C<ev_default_loop>, but always creates a new event loop that is
164	always distinct from the default loop. Unlike the default loop, it cannot	390	always distinct from the default loop. Unlike the default loop, it cannot
165	handle signal and child watchers, and attempts to do so will be greeted by	391	handle signal and child watchers, and attempts to do so will be greeted by
166	undefined behaviour (or a failed assertion if assertions are enabled).	392	undefined behaviour (or a failed assertion if assertions are enabled).
167		393
		394	Example: Try to create a event loop that uses epoll and nothing else.
		395
		396	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		397	if (!epoller)
		398	fatal ("no epoll found here, maybe it hides under your chair");
		399
168	=item ev_default_destroy ()	400	=item ev_default_destroy ()
169		401
170	Destroys the default loop again (frees all memory and kernel state	402	Destroys the default loop again (frees all memory and kernel state
171	etc.). This stops all registered event watchers (by not touching them in	403	etc.). None of the active event watchers will be stopped in the normal
172	any way whatsoever, although you cannot rely on this :).	404	sense, so e.g. C<ev_is_active> might still return true. It is your
		405	responsibility to either stop all watchers cleanly yoursef I<before>
		406	calling this function, or cope with the fact afterwards (which is usually
		407	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		408	for example).
173		409
174	=item ev_loop_destroy (loop)	410	=item ev_loop_destroy (loop)
175		411
176	Like C<ev_default_destroy>, but destroys an event loop created by an	412	Like C<ev_default_destroy>, but destroys an event loop created by an
177	earlier call to C<ev_loop_new>.	413	earlier call to C<ev_loop_new>.
…		…
181	This function reinitialises the kernel state for backends that have	417	This function reinitialises the kernel state for backends that have
182	one. Despite the name, you can call it anytime, but it makes most sense	418	one. Despite the name, you can call it anytime, but it makes most sense
183	after forking, in either the parent or child process (or both, but that	419	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	420	again makes little sense).
185		421
186	You I<must> call this function after forking if and only if you want to	422	You I<must> call this function in the child process after forking if and
187	use the event library in both processes. If you just fork+exec, you don't	423	only if you want to use the event library in both processes. If you just
188	have to call it.	424	fork+exec, you don't have to call it.
189		425
190	The function itself is quite fast and it's usually not a problem to call	426	The function itself is quite fast and it's usually not a problem to call
191	it just in case after a fork. To make this easy, the function will fit in	427	it just in case after a fork. To make this easy, the function will fit in
192	quite nicely into a call to C<pthread_atfork>:	428	quite nicely into a call to C<pthread_atfork>:
193		429
194	pthread_atfork (0, 0, ev_default_fork);	430	pthread_atfork (0, 0, ev_default_fork);
195		431
		432	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		433	without calling this function, so if you force one of those backends you
		434	do not need to care.
		435
196	=item ev_loop_fork (loop)	436	=item ev_loop_fork (loop)
197		437
198	Like C<ev_default_fork>, but acts on an event loop created by	438	Like C<ev_default_fork>, but acts on an event loop created by
199	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	439	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
200	after fork, and how you do this is entirely your own problem.	440	after fork, and how you do this is entirely your own problem.
201		441
		442	=item unsigned int ev_loop_count (loop)
		443
		444	Returns the count of loop iterations for the loop, which is identical to
		445	the number of times libev did poll for new events. It starts at C<0> and
		446	happily wraps around with enough iterations.
		447
		448	This value can sometimes be useful as a generation counter of sorts (it
		449	"ticks" the number of loop iterations), as it roughly corresponds with
		450	C<ev_prepare> and C<ev_check> calls.
		451
202	=item unsigned int ev_method (loop)	452	=item unsigned int ev_backend (loop)
203		453
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	454	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	455	use.
206		456
207	=item ev_tstamp ev_now (loop)	457	=item ev_tstamp ev_now (loop)
208		458
209	Returns the current "event loop time", which is the time the event loop	459	Returns the current "event loop time", which is the time the event loop
210	got events and started processing them. This timestamp does not change	460	received events and started processing them. This timestamp does not
211	as long as callbacks are being processed, and this is also the base time	461	change as long as callbacks are being processed, and this is also the base
212	used for relative timers. You can treat it as the timestamp of the event	462	time used for relative timers. You can treat it as the timestamp of the
213	occuring (or more correctly, the mainloop finding out about it).	463	event occuring (or more correctly, libev finding out about it).
214		464
215	=item ev_loop (loop, int flags)	465	=item ev_loop (loop, int flags)
216		466
217	Finally, this is it, the event handler. This function usually is called	467	Finally, this is it, the event handler. This function usually is called
218	after you initialised all your watchers and you want to start handling	468	after you initialised all your watchers and you want to start handling
219	events.	469	events.
220		470
221	If the flags argument is specified as 0, it will not return until either	471	If the flags argument is specified as C<0>, it will not return until
222	no event watchers are active anymore or C<ev_unloop> was called.	472	either no event watchers are active anymore or C<ev_unloop> was called.
		473
		474	Please note that an explicit C<ev_unloop> is usually better than
		475	relying on all watchers to be stopped when deciding when a program has
		476	finished (especially in interactive programs), but having a program that
		477	automatically loops as long as it has to and no longer by virtue of
		478	relying on its watchers stopping correctly is a thing of beauty.
223		479
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	480	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
225	those events and any outstanding ones, but will not block your process in	481	those events and any outstanding ones, but will not block your process in
226	case there are no events and will return after one iteration of the loop.	482	case there are no events and will return after one iteration of the loop.
227		483
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	484	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
229	neccessary) and will handle those and any outstanding ones. It will block	485	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives, and will return after	486	your process until at least one new event arrives, and will return after
231	one iteration of the loop.	487	one iteration of the loop. This is useful if you are waiting for some
		488	external event in conjunction with something not expressible using other
		489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		490	usually a better approach for this kind of thing.
232		491
233	This flags value could be used to implement alternative looping	492	Here are the gory details of what C<ev_loop> does:
234	constructs, but the C<prepare> and C<check> watchers provide a better and	493
235	more generic mechanism.	494	- Before the first iteration, call any pending watchers.
		495	* If there are no active watchers (reference count is zero), return.
		496	- Queue all prepare watchers and then call all outstanding watchers.
		497	- If we have been forked, recreate the kernel state.
		498	- Update the kernel state with all outstanding changes.
		499	- Update the "event loop time".
		500	- Calculate for how long to block.
		501	- Block the process, waiting for any events.
		502	- Queue all outstanding I/O (fd) events.
		503	- Update the "event loop time" and do time jump handling.
		504	- Queue all outstanding timers.
		505	- Queue all outstanding periodics.
		506	- If no events are pending now, queue all idle watchers.
		507	- Queue all check watchers.
		508	- Call all queued watchers in reverse order (i.e. check watchers first).
		509	Signals and child watchers are implemented as I/O watchers, and will
		510	be handled here by queueing them when their watcher gets executed.
		511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		512	were used, return, otherwise continue with step *.
		513
		514	Example: Queue some jobs and then loop until no events are outsanding
		515	anymore.
		516
		517	... queue jobs here, make sure they register event watchers as long
		518	... as they still have work to do (even an idle watcher will do..)
		519	ev_loop (my_loop, 0);
		520	... jobs done. yeah!
236		521
237	=item ev_unloop (loop, how)	522	=item ev_unloop (loop, how)
238		523
239	Can be used to make a call to C<ev_loop> return early (but only after it	524	Can be used to make a call to C<ev_loop> return early (but only after it
240	has processed all outstanding events). The C<how> argument must be either	525	has processed all outstanding events). The C<how> argument must be either
241	C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or	526	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
242	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	527	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
243		528
244	=item ev_ref (loop)	529	=item ev_ref (loop)
245		530
246	=item ev_unref (loop)	531	=item ev_unref (loop)
…		…
254	visible to the libev user and should not keep C<ev_loop> from exiting if	539	visible to the libev user and should not keep C<ev_loop> from exiting if
255	no event watchers registered by it are active. It is also an excellent	540	no event watchers registered by it are active. It is also an excellent
256	way to do this for generic recurring timers or from within third-party	541	way to do this for generic recurring timers or from within third-party
257	libraries. Just remember to I<unref after start> and I<ref before stop>.	542	libraries. Just remember to I<unref after start> and I<ref before stop>.
258		543
		544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		545	running when nothing else is active.
		546
		547	struct ev_signal exitsig;
		548	ev_signal_init (&exitsig, sig_cb, SIGINT);
		549	ev_signal_start (loop, &exitsig);
		550	evf_unref (loop);
		551
		552	Example: For some weird reason, unregister the above signal handler again.
		553
		554	ev_ref (loop);
		555	ev_signal_stop (loop, &exitsig);
		556
259	=back	557	=back
		558
260		559
261	=head1 ANATOMY OF A WATCHER	560	=head1 ANATOMY OF A WATCHER
262		561
263	A watcher is a structure that you create and register to record your	562	A watcher is a structure that you create and register to record your
264	interest in some event. For instance, if you want to wait for STDIN to	563	interest in some event. For instance, if you want to wait for STDIN to
…		…
297	*) >>), and you can stop watching for events at any time by calling the	596	*) >>), and you can stop watching for events at any time by calling the
298	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	597	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
299		598
300	As long as your watcher is active (has been started but not stopped) you	599	As long as your watcher is active (has been started but not stopped) you
301	must not touch the values stored in it. Most specifically you must never	600	must not touch the values stored in it. Most specifically you must never
302	reinitialise it or call its set method.	601	reinitialise it or call its C<set> macro.
303
304	You can check whether an event is active by calling the C<ev_is_active
305	(watcher *)> macro. To see whether an event is outstanding (but the
306	callback for it has not been called yet) you can use the C<ev_is_pending
307	(watcher *)> macro.
308		602
309	Each and every callback receives the event loop pointer as first, the	603	Each and every callback receives the event loop pointer as first, the
310	registered watcher structure as second, and a bitset of received events as	604	registered watcher structure as second, and a bitset of received events as
311	third argument.	605	third argument.
312		606
…		…
336	The signal specified in the C<ev_signal> watcher has been received by a thread.	630	The signal specified in the C<ev_signal> watcher has been received by a thread.
337		631
338	=item C<EV_CHILD>	632	=item C<EV_CHILD>
339		633
340	The pid specified in the C<ev_child> watcher has received a status change.	634	The pid specified in the C<ev_child> watcher has received a status change.
		635
		636	=item C<EV_STAT>
		637
		638	The path specified in the C<ev_stat> watcher changed its attributes somehow.
341		639
342	=item C<EV_IDLE>	640	=item C<EV_IDLE>
343		641
344	The C<ev_idle> watcher has determined that you have nothing better to do.	642	The C<ev_idle> watcher has determined that you have nothing better to do.
345		643
…		…
353	received events. Callbacks of both watcher types can start and stop as	651	received events. Callbacks of both watcher types can start and stop as
354	many watchers as they want, and all of them will be taken into account	652	many watchers as they want, and all of them will be taken into account
355	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	653	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
356	C<ev_loop> from blocking).	654	C<ev_loop> from blocking).
357		655
		656	=item C<EV_EMBED>
		657
		658	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		659
		660	=item C<EV_FORK>
		661
		662	The event loop has been resumed in the child process after fork (see
		663	C<ev_fork>).
		664
358	=item C<EV_ERROR>	665	=item C<EV_ERROR>
359		666
360	An unspecified error has occured, the watcher has been stopped. This might	667	An unspecified error has occured, the watcher has been stopped. This might
361	happen because the watcher could not be properly started because libev	668	happen because the watcher could not be properly started because libev
362	ran out of memory, a file descriptor was found to be closed or any other	669	ran out of memory, a file descriptor was found to be closed or any other
…		…
368	your callbacks is well-written it can just attempt the operation and cope	675	your callbacks is well-written it can just attempt the operation and cope
369	with the error from read() or write(). This will not work in multithreaded	676	with the error from read() or write(). This will not work in multithreaded
370	programs, though, so beware.	677	programs, though, so beware.
371		678
372	=back	679	=back
		680
		681	=head2 GENERIC WATCHER FUNCTIONS
		682
		683	In the following description, C<TYPE> stands for the watcher type,
		684	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		685
		686	=over 4
		687
		688	=item C<ev_init> (ev_TYPE *watcher, callback)
		689
		690	This macro initialises the generic portion of a watcher. The contents
		691	of the watcher object can be arbitrary (so C<malloc> will do). Only
		692	the generic parts of the watcher are initialised, you I<need> to call
		693	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		694	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		695	which rolls both calls into one.
		696
		697	You can reinitialise a watcher at any time as long as it has been stopped
		698	(or never started) and there are no pending events outstanding.
		699
		700	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		701	int revents)>.
		702
		703	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		704
		705	This macro initialises the type-specific parts of a watcher. You need to
		706	call C<ev_init> at least once before you call this macro, but you can
		707	call C<ev_TYPE_set> any number of times. You must not, however, call this
		708	macro on a watcher that is active (it can be pending, however, which is a
		709	difference to the C<ev_init> macro).
		710
		711	Although some watcher types do not have type-specific arguments
		712	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		713
		714	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		715
		716	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		717	calls into a single call. This is the most convinient method to initialise
		718	a watcher. The same limitations apply, of course.
		719
		720	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		721
		722	Starts (activates) the given watcher. Only active watchers will receive
		723	events. If the watcher is already active nothing will happen.
		724
		725	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		726
		727	Stops the given watcher again (if active) and clears the pending
		728	status. It is possible that stopped watchers are pending (for example,
		729	non-repeating timers are being stopped when they become pending), but
		730	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		731	you want to free or reuse the memory used by the watcher it is therefore a
		732	good idea to always call its C<ev_TYPE_stop> function.
		733
		734	=item bool ev_is_active (ev_TYPE *watcher)
		735
		736	Returns a true value iff the watcher is active (i.e. it has been started
		737	and not yet been stopped). As long as a watcher is active you must not modify
		738	it.
		739
		740	=item bool ev_is_pending (ev_TYPE *watcher)
		741
		742	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		743	events but its callback has not yet been invoked). As long as a watcher
		744	is pending (but not active) you must not call an init function on it (but
		745	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		746	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		747	it).
		748
		749	=item callback ev_cb (ev_TYPE *watcher)
		750
		751	Returns the callback currently set on the watcher.
		752
		753	=item ev_cb_set (ev_TYPE *watcher, callback)
		754
		755	Change the callback. You can change the callback at virtually any time
		756	(modulo threads).
		757
		758	=item ev_set_priority (ev_TYPE *watcher, priority)
		759
		760	=item int ev_priority (ev_TYPE *watcher)
		761
		762	Set and query the priority of the watcher. The priority is a small
		763	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		764	(default: C<-2>). Pending watchers with higher priority will be invoked
		765	before watchers with lower priority, but priority will not keep watchers
		766	from being executed (except for C<ev_idle> watchers).
		767
		768	This means that priorities are I<only> used for ordering callback
		769	invocation after new events have been received. This is useful, for
		770	example, to reduce latency after idling, or more often, to bind two
		771	watchers on the same event and make sure one is called first.
		772
		773	If you need to suppress invocation when higher priority events are pending
		774	you need to look at C<ev_idle> watchers, which provide this functionality.
		775
		776	You I<must not> change the priority of a watcher as long as it is active or
		777	pending.
		778
		779	The default priority used by watchers when no priority has been set is
		780	always C<0>, which is supposed to not be too high and not be too low :).
		781
		782	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		783	fine, as long as you do not mind that the priority value you query might
		784	or might not have been adjusted to be within valid range.
		785
		786	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		787
		788	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		789	C<loop> nor C<revents> need to be valid as long as the watcher callback
		790	can deal with that fact.
		791
		792	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		793
		794	If the watcher is pending, this function returns clears its pending status
		795	and returns its C<revents> bitset (as if its callback was invoked). If the
		796	watcher isn't pending it does nothing and returns C<0>.
		797
		798	=back
		799
373		800
374	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
375		802
376	Each watcher has, by default, a member C<void *data> that you can change	803	Each watcher has, by default, a member C<void *data> that you can change
377	and read at any time, libev will completely ignore it. This can be used	804	and read at any time, libev will completely ignore it. This can be used
…		…
395	{	822	{
396	struct my_io *w = (struct my_io *)w_;	823	struct my_io *w = (struct my_io *)w_;
397	...	824	...
398	}	825	}
399		826
400	More interesting and less C-conformant ways of catsing your callback type	827	More interesting and less C-conformant ways of casting your callback type
401	have been omitted....	828	instead have been omitted.
		829
		830	Another common scenario is having some data structure with multiple
		831	watchers:
		832
		833	struct my_biggy
		834	{
		835	int some_data;
		836	ev_timer t1;
		837	ev_timer t2;
		838	}
		839
		840	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		841	you need to use C<offsetof>:
		842
		843	#include <stddef.h>
		844
		845	static void
		846	t1_cb (EV_P_ struct ev_timer *w, int revents)
		847	{
		848	struct my_biggy big = (struct my_biggy *
		849	(((char *)w) - offsetof (struct my_biggy, t1));
		850	}
		851
		852	static void
		853	t2_cb (EV_P_ struct ev_timer *w, int revents)
		854	{
		855	struct my_biggy big = (struct my_biggy *
		856	(((char *)w) - offsetof (struct my_biggy, t2));
		857	}
402		858
403		859
404	=head1 WATCHER TYPES	860	=head1 WATCHER TYPES
405		861
406	This section describes each watcher in detail, but will not repeat	862	This section describes each watcher in detail, but will not repeat
407	information given in the last section.	863	information given in the last section. Any initialisation/set macros,
		864	functions and members specific to the watcher type are explained.
408		865
		866	Members are additionally marked with either I<[read-only]>, meaning that,
		867	while the watcher is active, you can look at the member and expect some
		868	sensible content, but you must not modify it (you can modify it while the
		869	watcher is stopped to your hearts content), or I<[read-write]>, which
		870	means you can expect it to have some sensible content while the watcher
		871	is active, but you can also modify it. Modifying it may not do something
		872	sensible or take immediate effect (or do anything at all), but libev will
		873	not crash or malfunction in any way.
		874
		875
409	=head2 C<ev_io> - is this file descriptor readable or writable	876	=head2 C<ev_io> - is this file descriptor readable or writable?
410		877
411	I/O watchers check whether a file descriptor is readable or writable	878	I/O watchers check whether a file descriptor is readable or writable
412	in each iteration of the event loop (This behaviour is called	879	in each iteration of the event loop, or, more precisely, when reading
413	level-triggering because you keep receiving events as long as the	880	would not block the process and writing would at least be able to write
414	condition persists. Remember you can stop the watcher if you don't want to	881	some data. This behaviour is called level-triggering because you keep
415	act on the event and neither want to receive future events).	882	receiving events as long as the condition persists. Remember you can stop
		883	the watcher if you don't want to act on the event and neither want to
		884	receive future events.
416		885
417	In general you can register as many read and/or write event watchers oer	886	In general you can register as many read and/or write event watchers per
418	fd as you want (as long as you don't confuse yourself). Setting all file	887	fd as you want (as long as you don't confuse yourself). Setting all file
419	descriptors to non-blocking mode is also usually a good idea (but not	888	descriptors to non-blocking mode is also usually a good idea (but not
420	required if you know what you are doing).	889	required if you know what you are doing).
421		890
422	You have to be careful with dup'ed file descriptors, though. Some backends	891	You have to be careful with dup'ed file descriptors, though. Some backends
423	(the linux epoll backend is a notable example) cannot handle dup'ed file	892	(the linux epoll backend is a notable example) cannot handle dup'ed file
424	descriptors correctly if you register interest in two or more fds pointing	893	descriptors correctly if you register interest in two or more fds pointing
425	to the same file/socket etc. description.	894	to the same underlying file/socket/etc. description (that is, they share
		895	the same underlying "file open").
426		896
427	If you must do this, then force the use of a known-to-be-good backend	897	If you must do this, then force the use of a known-to-be-good backend
428	(at the time of this writing, this includes only EVMETHOD_SELECT and	898	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
429	EVMETHOD_POLL).	899	C<EVBACKEND_POLL>).
		900
		901	Another thing you have to watch out for is that it is quite easy to
		902	receive "spurious" readyness notifications, that is your callback might
		903	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		904	because there is no data. Not only are some backends known to create a
		905	lot of those (for example solaris ports), it is very easy to get into
		906	this situation even with a relatively standard program structure. Thus
		907	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		908	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		909
		910	If you cannot run the fd in non-blocking mode (for example you should not
		911	play around with an Xlib connection), then you have to seperately re-test
		912	whether a file descriptor is really ready with a known-to-be good interface
		913	such as poll (fortunately in our Xlib example, Xlib already does this on
		914	its own, so its quite safe to use).
		915
		916	=head3 The special problem of disappearing file descriptors
		917
		918	Some backends (e.g kqueue, epoll) need to be told about closing a file
		919	descriptor (either by calling C<close> explicitly or by any other means,
		920	such as C<dup>). The reason is that you register interest in some file
		921	descriptor, but when it goes away, the operating system will silently drop
		922	this interest. If another file descriptor with the same number then is
		923	registered with libev, there is no efficient way to see that this is, in
		924	fact, a different file descriptor.
		925
		926	To avoid having to explicitly tell libev about such cases, libev follows
		927	the following policy: Each time C<ev_io_set> is being called, libev
		928	will assume that this is potentially a new file descriptor, otherwise
		929	it is assumed that the file descriptor stays the same. That means that
		930	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		931	descriptor even if the file descriptor number itself did not change.
		932
		933	This is how one would do it normally anyway, the important point is that
		934	the libev application should not optimise around libev but should leave
		935	optimisations to libev.
		936
		937
		938	=head3 Watcher-Specific Functions
430		939
431	=over 4	940	=over 4
432		941
433	=item ev_io_init (ev_io *, callback, int fd, int events)	942	=item ev_io_init (ev_io *, callback, int fd, int events)
434		943
435	=item ev_io_set (ev_io *, int fd, int events)	944	=item ev_io_set (ev_io *, int fd, int events)
436		945
437	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	946	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
438	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	947	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
439	EV_WRITE> to receive the given events.	948	C<EV_READ | EV_WRITE> to receive the given events.
		949
		950	=item int fd [read-only]
		951
		952	The file descriptor being watched.
		953
		954	=item int events [read-only]
		955
		956	The events being watched.
440		957
441	=back	958	=back
442		959
		960	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		961	readable, but only once. Since it is likely line-buffered, you could
		962	attempt to read a whole line in the callback.
		963
		964	static void
		965	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		966	{
		967	ev_io_stop (loop, w);
		968	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		969	}
		970
		971	...
		972	struct ev_loop *loop = ev_default_init (0);
		973	struct ev_io stdin_readable;
		974	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		975	ev_io_start (loop, &stdin_readable);
		976	ev_loop (loop, 0);
		977
		978
443	=head2 C<ev_timer> - relative and optionally recurring timeouts	979	=head2 C<ev_timer> - relative and optionally repeating timeouts
444		980
445	Timer watchers are simple relative timers that generate an event after a	981	Timer watchers are simple relative timers that generate an event after a
446	given time, and optionally repeating in regular intervals after that.	982	given time, and optionally repeating in regular intervals after that.
447		983
448	The timers are based on real time, that is, if you register an event that	984	The timers are based on real time, that is, if you register an event that
449	times out after an hour and youreset your system clock to last years	985	times out after an hour and you reset your system clock to last years
450	time, it will still time out after (roughly) and hour. "Roughly" because	986	time, it will still time out after (roughly) and hour. "Roughly" because
451	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	987	detecting time jumps is hard, and some inaccuracies are unavoidable (the
452	monotonic clock option helps a lot here).	988	monotonic clock option helps a lot here).
453		989
454	The relative timeouts are calculated relative to the C<ev_now ()>	990	The relative timeouts are calculated relative to the C<ev_now ()>
455	time. This is usually the right thing as this timestamp refers to the time	991	time. This is usually the right thing as this timestamp refers to the time
456	of the event triggering whatever timeout you are modifying/starting. If	992	of the event triggering whatever timeout you are modifying/starting. If
457	you suspect event processing to be delayed and you *need* to base the timeout	993	you suspect event processing to be delayed and you I<need> to base the timeout
458	ion the current time, use something like this to adjust for this:	994	on the current time, use something like this to adjust for this:
459		995
460	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	996	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		997
		998	The callback is guarenteed to be invoked only when its timeout has passed,
		999	but if multiple timers become ready during the same loop iteration then
		1000	order of execution is undefined.
		1001
		1002	=head3 Watcher-Specific Functions and Data Members
461		1003
462	=over 4	1004	=over 4
463		1005
464	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1006	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
465		1007
…		…
471	later, again, and again, until stopped manually.	1013	later, again, and again, until stopped manually.
472		1014
473	The timer itself will do a best-effort at avoiding drift, that is, if you	1015	The timer itself will do a best-effort at avoiding drift, that is, if you
474	configure a timer to trigger every 10 seconds, then it will trigger at	1016	configure a timer to trigger every 10 seconds, then it will trigger at
475	exactly 10 second intervals. If, however, your program cannot keep up with	1017	exactly 10 second intervals. If, however, your program cannot keep up with
476	the timer (ecause it takes longer than those 10 seconds to do stuff) the	1018	the timer (because it takes longer than those 10 seconds to do stuff) the
477	timer will not fire more than once per event loop iteration.	1019	timer will not fire more than once per event loop iteration.
478		1020
479	=item ev_timer_again (loop)	1021	=item ev_timer_again (loop)
480		1022
481	This will act as if the timer timed out and restart it again if it is	1023	This will act as if the timer timed out and restart it again if it is
482	repeating. The exact semantics are:	1024	repeating. The exact semantics are:
483		1025
		1026	If the timer is pending, its pending status is cleared.
		1027
484	If the timer is started but nonrepeating, stop it.	1028	If the timer is started but nonrepeating, stop it (as if it timed out).
485		1029
486	If the timer is repeating, either start it if necessary (with the repeat	1030	If the timer is repeating, either start it if necessary (with the
487	value), or reset the running timer to the repeat value.	1031	C<repeat> value), or reset the running timer to the C<repeat> value.
488		1032
489	This sounds a bit complicated, but here is a useful and typical	1033	This sounds a bit complicated, but here is a useful and typical
490	example: Imagine you have a tcp connection and you want a so-called idle	1034	example: Imagine you have a tcp connection and you want a so-called idle
491	timeout, that is, you want to be called when there have been, say, 60	1035	timeout, that is, you want to be called when there have been, say, 60
492	seconds of inactivity on the socket. The easiest way to do this is to	1036	seconds of inactivity on the socket. The easiest way to do this is to
493	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1037	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
494	time you successfully read or write some data. If you go into an idle	1038	C<ev_timer_again> each time you successfully read or write some data. If
495	state where you do not expect data to travel on the socket, you can stop	1039	you go into an idle state where you do not expect data to travel on the
496	the timer, and again will automatically restart it if need be.	1040	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1041	automatically restart it if need be.
		1042
		1043	That means you can ignore the C<after> value and C<ev_timer_start>
		1044	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1045
		1046	ev_timer_init (timer, callback, 0., 5.);
		1047	ev_timer_again (loop, timer);
		1048	...
		1049	timer->again = 17.;
		1050	ev_timer_again (loop, timer);
		1051	...
		1052	timer->again = 10.;
		1053	ev_timer_again (loop, timer);
		1054
		1055	This is more slightly efficient then stopping/starting the timer each time
		1056	you want to modify its timeout value.
		1057
		1058	=item ev_tstamp repeat [read-write]
		1059
		1060	The current C<repeat> value. Will be used each time the watcher times out
		1061	or C<ev_timer_again> is called and determines the next timeout (if any),
		1062	which is also when any modifications are taken into account.
497		1063
498	=back	1064	=back
499		1065
		1066	Example: Create a timer that fires after 60 seconds.
		1067
		1068	static void
		1069	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1070	{
		1071	.. one minute over, w is actually stopped right here
		1072	}
		1073
		1074	struct ev_timer mytimer;
		1075	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1076	ev_timer_start (loop, &mytimer);
		1077
		1078	Example: Create a timeout timer that times out after 10 seconds of
		1079	inactivity.
		1080
		1081	static void
		1082	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1083	{
		1084	.. ten seconds without any activity
		1085	}
		1086
		1087	struct ev_timer mytimer;
		1088	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1089	ev_timer_again (&mytimer); /* start timer */
		1090	ev_loop (loop, 0);
		1091
		1092	// and in some piece of code that gets executed on any "activity":
		1093	// reset the timeout to start ticking again at 10 seconds
		1094	ev_timer_again (&mytimer);
		1095
		1096
500	=head2 C<ev_periodic> - to cron or not to cron	1097	=head2 C<ev_periodic> - to cron or not to cron?
501		1098
502	Periodic watchers are also timers of a kind, but they are very versatile	1099	Periodic watchers are also timers of a kind, but they are very versatile
503	(and unfortunately a bit complex).	1100	(and unfortunately a bit complex).
504		1101
505	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1102	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
506	but on wallclock time (absolute time). You can tell a periodic watcher	1103	but on wallclock time (absolute time). You can tell a periodic watcher
507	to trigger "at" some specific point in time. For example, if you tell a	1104	to trigger "at" some specific point in time. For example, if you tell a
508	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1105	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
509	+ 10.>) and then reset your system clock to the last year, then it will	1106	+ 10.>) and then reset your system clock to the last year, then it will
510	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1107	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
511	roughly 10 seconds later and of course not if you reset your system time	1108	roughly 10 seconds later).
512	again).
513		1109
514	They can also be used to implement vastly more complex timers, such as	1110	They can also be used to implement vastly more complex timers, such as
515	triggering an event on eahc midnight, local time.	1111	triggering an event on each midnight, local time or other, complicated,
		1112	rules.
		1113
		1114	As with timers, the callback is guarenteed to be invoked only when the
		1115	time (C<at>) has been passed, but if multiple periodic timers become ready
		1116	during the same loop iteration then order of execution is undefined.
		1117
		1118	=head3 Watcher-Specific Functions and Data Members
516		1119
517	=over 4	1120	=over 4
518		1121
519	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1122	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
520		1123
521	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1124	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
522		1125
523	Lots of arguments, lets sort it out... There are basically three modes of	1126	Lots of arguments, lets sort it out... There are basically three modes of
524	operation, and we will explain them from simplest to complex:	1127	operation, and we will explain them from simplest to complex:
525		1128
526
527	=over 4	1129	=over 4
528		1130
529	=item * absolute timer (interval = reschedule_cb = 0)	1131	=item * absolute timer (at = time, interval = reschedule_cb = 0)
530		1132
531	In this configuration the watcher triggers an event at the wallclock time	1133	In this configuration the watcher triggers an event at the wallclock time
532	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1134	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
533	that is, if it is to be run at January 1st 2011 then it will run when the	1135	that is, if it is to be run at January 1st 2011 then it will run when the
534	system time reaches or surpasses this time.	1136	system time reaches or surpasses this time.
535		1137
536	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1138	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
537		1139
538	In this mode the watcher will always be scheduled to time out at the next	1140	In this mode the watcher will always be scheduled to time out at the next
539	C<at + N * interval> time (for some integer N) and then repeat, regardless	1141	C<at + N * interval> time (for some integer N, which can also be negative)
540	of any time jumps.	1142	and then repeat, regardless of any time jumps.
541		1143
542	This can be used to create timers that do not drift with respect to system	1144	This can be used to create timers that do not drift with respect to system
543	time:	1145	time:
544		1146
545	ev_periodic_set (&periodic, 0., 3600., 0);	1147	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
551		1153
552	Another way to think about it (for the mathematically inclined) is that	1154	Another way to think about it (for the mathematically inclined) is that
553	C<ev_periodic> will try to run the callback in this mode at the next possible	1155	C<ev_periodic> will try to run the callback in this mode at the next possible
554	time where C<time = at (mod interval)>, regardless of any time jumps.	1156	time where C<time = at (mod interval)>, regardless of any time jumps.
555		1157
		1158	For numerical stability it is preferable that the C<at> value is near
		1159	C<ev_now ()> (the current time), but there is no range requirement for
		1160	this value.
		1161
556	=item * manual reschedule mode (reschedule_cb = callback)	1162	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
557		1163
558	In this mode the values for C<interval> and C<at> are both being	1164	In this mode the values for C<interval> and C<at> are both being
559	ignored. Instead, each time the periodic watcher gets scheduled, the	1165	ignored. Instead, each time the periodic watcher gets scheduled, the
560	reschedule callback will be called with the watcher as first, and the	1166	reschedule callback will be called with the watcher as first, and the
561	current time as second argument.	1167	current time as second argument.
562		1168
563	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	1169	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
564	periodic watcher, ever, or make any event loop modifications>. If you need	1170	ever, or make any event loop modifications>. If you need to stop it,
565	to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards.	1171	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
566		1172	starting an C<ev_prepare> watcher, which is legal).
567	Also, I<< this callback must always return a time that is later than the
568	passed C<now> value >>. Not even C<now> itself will be ok.
569		1173
570	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1174	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
571	ev_tstamp now)>, e.g.:	1175	ev_tstamp now)>, e.g.:
572		1176
573	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1177	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
578	It must return the next time to trigger, based on the passed time value	1182	It must return the next time to trigger, based on the passed time value
579	(that is, the lowest time value larger than to the second argument). It	1183	(that is, the lowest time value larger than to the second argument). It
580	will usually be called just before the callback will be triggered, but	1184	will usually be called just before the callback will be triggered, but
581	might be called at other times, too.	1185	might be called at other times, too.
582		1186
		1187	NOTE: I<< This callback must always return a time that is later than the
		1188	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		1189
583	This can be used to create very complex timers, such as a timer that	1190	This can be used to create very complex timers, such as a timer that
584	triggers on each midnight, local time. To do this, you would calculate the	1191	triggers on each midnight, local time. To do this, you would calculate the
585	next midnight after C<now> and return the timestamp value for this. How you do this	1192	next midnight after C<now> and return the timestamp value for this. How
586	is, again, up to you (but it is not trivial).	1193	you do this is, again, up to you (but it is not trivial, which is the main
		1194	reason I omitted it as an example).
587		1195
588	=back	1196	=back
589		1197
590	=item ev_periodic_again (loop, ev_periodic *)	1198	=item ev_periodic_again (loop, ev_periodic *)
591		1199
592	Simply stops and restarts the periodic watcher again. This is only useful	1200	Simply stops and restarts the periodic watcher again. This is only useful
593	when you changed some parameters or the reschedule callback would return	1201	when you changed some parameters or the reschedule callback would return
594	a different time than the last time it was called (e.g. in a crond like	1202	a different time than the last time it was called (e.g. in a crond like
595	program when the crontabs have changed).	1203	program when the crontabs have changed).
596		1204
		1205	=item ev_tstamp offset [read-write]
		1206
		1207	When repeating, this contains the offset value, otherwise this is the
		1208	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1209
		1210	Can be modified any time, but changes only take effect when the periodic
		1211	timer fires or C<ev_periodic_again> is being called.
		1212
		1213	=item ev_tstamp interval [read-write]
		1214
		1215	The current interval value. Can be modified any time, but changes only
		1216	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1217	called.
		1218
		1219	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1220
		1221	The current reschedule callback, or C<0>, if this functionality is
		1222	switched off. Can be changed any time, but changes only take effect when
		1223	the periodic timer fires or C<ev_periodic_again> is being called.
		1224
597	=back	1225	=back
598		1226
		1227	Example: Call a callback every hour, or, more precisely, whenever the
		1228	system clock is divisible by 3600. The callback invocation times have
		1229	potentially a lot of jittering, but good long-term stability.
		1230
		1231	static void
		1232	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1233	{
		1234	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1235	}
		1236
		1237	struct ev_periodic hourly_tick;
		1238	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1239	ev_periodic_start (loop, &hourly_tick);
		1240
		1241	Example: The same as above, but use a reschedule callback to do it:
		1242
		1243	#include <math.h>
		1244
		1245	static ev_tstamp
		1246	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1247	{
		1248	return fmod (now, 3600.) + 3600.;
		1249	}
		1250
		1251	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1252
		1253	Example: Call a callback every hour, starting now:
		1254
		1255	struct ev_periodic hourly_tick;
		1256	ev_periodic_init (&hourly_tick, clock_cb,
		1257	fmod (ev_now (loop), 3600.), 3600., 0);
		1258	ev_periodic_start (loop, &hourly_tick);
		1259
		1260
599	=head2 C<ev_signal> - signal me when a signal gets signalled	1261	=head2 C<ev_signal> - signal me when a signal gets signalled!
600		1262
601	Signal watchers will trigger an event when the process receives a specific	1263	Signal watchers will trigger an event when the process receives a specific
602	signal one or more times. Even though signals are very asynchronous, libev	1264	signal one or more times. Even though signals are very asynchronous, libev
603	will try it's best to deliver signals synchronously, i.e. as part of the	1265	will try it's best to deliver signals synchronously, i.e. as part of the
604	normal event processing, like any other event.	1266	normal event processing, like any other event.
…		…
608	with the kernel (thus it coexists with your own signal handlers as long	1270	with the kernel (thus it coexists with your own signal handlers as long
609	as you don't register any with libev). Similarly, when the last signal	1271	as you don't register any with libev). Similarly, when the last signal
610	watcher for a signal is stopped libev will reset the signal handler to	1272	watcher for a signal is stopped libev will reset the signal handler to
611	SIG_DFL (regardless of what it was set to before).	1273	SIG_DFL (regardless of what it was set to before).
612		1274
		1275	=head3 Watcher-Specific Functions and Data Members
		1276
613	=over 4	1277	=over 4
614		1278
615	=item ev_signal_init (ev_signal *, callback, int signum)	1279	=item ev_signal_init (ev_signal *, callback, int signum)
616		1280
617	=item ev_signal_set (ev_signal *, int signum)	1281	=item ev_signal_set (ev_signal *, int signum)
618		1282
619	Configures the watcher to trigger on the given signal number (usually one	1283	Configures the watcher to trigger on the given signal number (usually one
620	of the C<SIGxxx> constants).	1284	of the C<SIGxxx> constants).
621		1285
		1286	=item int signum [read-only]
		1287
		1288	The signal the watcher watches out for.
		1289
622	=back	1290	=back
623		1291
		1292
624	=head2 C<ev_child> - wait for pid status changes	1293	=head2 C<ev_child> - watch out for process status changes
625		1294
626	Child watchers trigger when your process receives a SIGCHLD in response to	1295	Child watchers trigger when your process receives a SIGCHLD in response to
627	some child status changes (most typically when a child of yours dies).	1296	some child status changes (most typically when a child of yours dies).
		1297
		1298	=head3 Watcher-Specific Functions and Data Members
628		1299
629	=over 4	1300	=over 4
630		1301
631	=item ev_child_init (ev_child *, callback, int pid)	1302	=item ev_child_init (ev_child *, callback, int pid)
632		1303
…		…
637	at the C<rstatus> member of the C<ev_child> watcher structure to see	1308	at the C<rstatus> member of the C<ev_child> watcher structure to see
638	the status word (use the macros from C<sys/wait.h> and see your systems	1309	the status word (use the macros from C<sys/wait.h> and see your systems
639	C<waitpid> documentation). The C<rpid> member contains the pid of the	1310	C<waitpid> documentation). The C<rpid> member contains the pid of the
640	process causing the status change.	1311	process causing the status change.
641		1312
		1313	=item int pid [read-only]
		1314
		1315	The process id this watcher watches out for, or C<0>, meaning any process id.
		1316
		1317	=item int rpid [read-write]
		1318
		1319	The process id that detected a status change.
		1320
		1321	=item int rstatus [read-write]
		1322
		1323	The process exit/trace status caused by C<rpid> (see your systems
		1324	C<waitpid> and C<sys/wait.h> documentation for details).
		1325
642	=back	1326	=back
643		1327
		1328	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1329
		1330	static void
		1331	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1332	{
		1333	ev_unloop (loop, EVUNLOOP_ALL);
		1334	}
		1335
		1336	struct ev_signal signal_watcher;
		1337	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1338	ev_signal_start (loop, &sigint_cb);
		1339
		1340
		1341	=head2 C<ev_stat> - did the file attributes just change?
		1342
		1343	This watches a filesystem path for attribute changes. That is, it calls
		1344	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1345	compared to the last time, invoking the callback if it did.
		1346
		1347	The path does not need to exist: changing from "path exists" to "path does
		1348	not exist" is a status change like any other. The condition "path does
		1349	not exist" is signified by the C<st_nlink> field being zero (which is
		1350	otherwise always forced to be at least one) and all the other fields of
		1351	the stat buffer having unspecified contents.
		1352
		1353	The path I<should> be absolute and I<must not> end in a slash. If it is
		1354	relative and your working directory changes, the behaviour is undefined.
		1355
		1356	Since there is no standard to do this, the portable implementation simply
		1357	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1358	can specify a recommended polling interval for this case. If you specify
		1359	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1360	unspecified default> value will be used (which you can expect to be around
		1361	five seconds, although this might change dynamically). Libev will also
		1362	impose a minimum interval which is currently around C<0.1>, but thats
		1363	usually overkill.
		1364
		1365	This watcher type is not meant for massive numbers of stat watchers,
		1366	as even with OS-supported change notifications, this can be
		1367	resource-intensive.
		1368
		1369	At the time of this writing, only the Linux inotify interface is
		1370	implemented (implementing kqueue support is left as an exercise for the
		1371	reader). Inotify will be used to give hints only and should not change the
		1372	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1373	to fall back to regular polling again even with inotify, but changes are
		1374	usually detected immediately, and if the file exists there will be no
		1375	polling.
		1376
		1377	=head3 Watcher-Specific Functions and Data Members
		1378
		1379	=over 4
		1380
		1381	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1382
		1383	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1384
		1385	Configures the watcher to wait for status changes of the given
		1386	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1387	be detected and should normally be specified as C<0> to let libev choose
		1388	a suitable value. The memory pointed to by C<path> must point to the same
		1389	path for as long as the watcher is active.
		1390
		1391	The callback will be receive C<EV_STAT> when a change was detected,
		1392	relative to the attributes at the time the watcher was started (or the
		1393	last change was detected).
		1394
		1395	=item ev_stat_stat (ev_stat *)
		1396
		1397	Updates the stat buffer immediately with new values. If you change the
		1398	watched path in your callback, you could call this fucntion to avoid
		1399	detecting this change (while introducing a race condition). Can also be
		1400	useful simply to find out the new values.
		1401
		1402	=item ev_statdata attr [read-only]
		1403
		1404	The most-recently detected attributes of the file. Although the type is of
		1405	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1406	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1407	was some error while C<stat>ing the file.
		1408
		1409	=item ev_statdata prev [read-only]
		1410
		1411	The previous attributes of the file. The callback gets invoked whenever
		1412	C<prev> != C<attr>.
		1413
		1414	=item ev_tstamp interval [read-only]
		1415
		1416	The specified interval.
		1417
		1418	=item const char *path [read-only]
		1419
		1420	The filesystem path that is being watched.
		1421
		1422	=back
		1423
		1424	Example: Watch C</etc/passwd> for attribute changes.
		1425
		1426	static void
		1427	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1428	{
		1429	/* /etc/passwd changed in some way */
		1430	if (w->attr.st_nlink)
		1431	{
		1432	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1433	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1434	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1435	}
		1436	else
		1437	/* you shalt not abuse printf for puts */
		1438	puts ("wow, /etc/passwd is not there, expect problems. "
		1439	"if this is windows, they already arrived\n");
		1440	}
		1441
		1442	...
		1443	ev_stat passwd;
		1444
		1445	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1446	ev_stat_start (loop, &passwd);
		1447
		1448
644	=head2 C<ev_idle> - when you've got nothing better to do	1449	=head2 C<ev_idle> - when you've got nothing better to do...
645		1450
646	Idle watchers trigger events when there are no other events are pending	1451	Idle watchers trigger events when no other events of the same or higher
647	(prepare, check and other idle watchers do not count). That is, as long	1452	priority are pending (prepare, check and other idle watchers do not
648	as your process is busy handling sockets or timeouts (or even signals,	1453	count).
649	imagine) it will not be triggered. But when your process is idle all idle	1454
650	watchers are being called again and again, once per event loop iteration -	1455	That is, as long as your process is busy handling sockets or timeouts
		1456	(or even signals, imagine) of the same or higher priority it will not be
		1457	triggered. But when your process is idle (or only lower-priority watchers
		1458	are pending), the idle watchers are being called once per event loop
651	until stopped, that is, or your process receives more events and becomes	1459	iteration - until stopped, that is, or your process receives more events
652	busy.	1460	and becomes busy again with higher priority stuff.
653		1461
654	The most noteworthy effect is that as long as any idle watchers are	1462	The most noteworthy effect is that as long as any idle watchers are
655	active, the process will not block when waiting for new events.	1463	active, the process will not block when waiting for new events.
656		1464
657	Apart from keeping your process non-blocking (which is a useful	1465	Apart from keeping your process non-blocking (which is a useful
658	effect on its own sometimes), idle watchers are a good place to do	1466	effect on its own sometimes), idle watchers are a good place to do
659	"pseudo-background processing", or delay processing stuff to after the	1467	"pseudo-background processing", or delay processing stuff to after the
660	event loop has handled all outstanding events.	1468	event loop has handled all outstanding events.
661		1469
		1470	=head3 Watcher-Specific Functions and Data Members
		1471
662	=over 4	1472	=over 4
663		1473
664	=item ev_idle_init (ev_signal *, callback)	1474	=item ev_idle_init (ev_signal *, callback)
665		1475
666	Initialises and configures the idle watcher - it has no parameters of any	1476	Initialises and configures the idle watcher - it has no parameters of any
667	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1477	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
668	believe me.	1478	believe me.
669		1479
670	=back	1480	=back
671		1481
		1482	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1483	callback, free it. Also, use no error checking, as usual.
		1484
		1485	static void
		1486	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1487	{
		1488	free (w);
		1489	// now do something you wanted to do when the program has
		1490	// no longer asnything immediate to do.
		1491	}
		1492
		1493	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1494	ev_idle_init (idle_watcher, idle_cb);
		1495	ev_idle_start (loop, idle_cb);
		1496
		1497
672	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1498	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
673		1499
674	Prepare and check watchers are usually (but not always) used in tandem:	1500	Prepare and check watchers are usually (but not always) used in tandem:
675	Prepare watchers get invoked before the process blocks and check watchers	1501	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.	1502	afterwards.
677		1503
		1504	You I<must not> call C<ev_loop> or similar functions that enter
		1505	the current event loop from either C<ev_prepare> or C<ev_check>
		1506	watchers. Other loops than the current one are fine, however. The
		1507	rationale behind this is that you do not need to check for recursion in
		1508	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1509	C<ev_check> so if you have one watcher of each kind they will always be
		1510	called in pairs bracketing the blocking call.
		1511
678	Their main purpose is to integrate other event mechanisms into libev. This	1512	Their main purpose is to integrate other event mechanisms into libev and
679	could be used, for example, to track variable changes, implement your own	1513	their use is somewhat advanced. This could be used, for example, to track
680	watchers, integrate net-snmp or a coroutine library and lots more.	1514	variable changes, implement your own watchers, integrate net-snmp or a
		1515	coroutine library and lots more. They are also occasionally useful if
		1516	you cache some data and want to flush it before blocking (for example,
		1517	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1518	watcher).
681		1519
682	This is done by examining in each prepare call which file descriptors need	1520	This is done by examining in each prepare call which file descriptors need
683	to be watched by the other library, registering C<ev_io> watchers for	1521	to be watched by the other library, registering C<ev_io> watchers for
684	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1522	them and starting an C<ev_timer> watcher for any timeouts (many libraries
685	provide just this functionality). Then, in the check watcher you check for	1523	provide just this functionality). Then, in the check watcher you check for
686	any events that occured (by checking the pending status of all watchers	1524	any events that occured (by checking the pending status of all watchers
687	and stopping them) and call back into the library. The I/O and timer	1525	and stopping them) and call back into the library. The I/O and timer
688	callbacks will never actually be called (but must be valid neverthelles,	1526	callbacks will never actually be called (but must be valid nevertheless,
689	because you never know, you know?).	1527	because you never know, you know?).
690		1528
691	As another example, the Perl Coro module uses these hooks to integrate	1529	As another example, the Perl Coro module uses these hooks to integrate
692	coroutines into libev programs, by yielding to other active coroutines	1530	coroutines into libev programs, by yielding to other active coroutines
693	during each prepare and only letting the process block if no coroutines	1531	during each prepare and only letting the process block if no coroutines
694	are ready to run (its actually more complicated, it only runs coroutines	1532	are ready to run (it's actually more complicated: it only runs coroutines
695	with priority higher than the event loop and one lower priority once,	1533	with priority higher than or equal to the event loop and one coroutine
696	using idle watchers to keep the event loop from blocking if lower-priority	1534	of lower priority, but only once, using idle watchers to keep the event
697	coroutines exist, thus mapping low-priority coroutines to idle/background	1535	loop from blocking if lower-priority coroutines are active, thus mapping
698	tasks).	1536	low-priority coroutines to idle/background tasks).
		1537
		1538	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1539	priority, to ensure that they are being run before any other watchers
		1540	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1541	too) should not activate ("feed") events into libev. While libev fully
		1542	supports this, they will be called before other C<ev_check> watchers did
		1543	their job. As C<ev_check> watchers are often used to embed other event
		1544	loops those other event loops might be in an unusable state until their
		1545	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1546	others).
		1547
		1548	=head3 Watcher-Specific Functions and Data Members
699		1549
700	=over 4	1550	=over 4
701		1551
702	=item ev_prepare_init (ev_prepare *, callback)	1552	=item ev_prepare_init (ev_prepare *, callback)
703		1553
…		…
707	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1557	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
708	macros, but using them is utterly, utterly and completely pointless.	1558	macros, but using them is utterly, utterly and completely pointless.
709		1559
710	=back	1560	=back
711		1561
		1562	There are a number of principal ways to embed other event loops or modules
		1563	into libev. Here are some ideas on how to include libadns into libev
		1564	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1565	use for an actually working example. Another Perl module named C<EV::Glib>
		1566	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1567	into the Glib event loop).
		1568
		1569	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1570	and in a check watcher, destroy them and call into libadns. What follows
		1571	is pseudo-code only of course. This requires you to either use a low
		1572	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1573	the callbacks for the IO/timeout watchers might not have been called yet.
		1574
		1575	static ev_io iow [nfd];
		1576	static ev_timer tw;
		1577
		1578	static void
		1579	io_cb (ev_loop *loop, ev_io *w, int revents)
		1580	{
		1581	}
		1582
		1583	// create io watchers for each fd and a timer before blocking
		1584	static void
		1585	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1586	{
		1587	int timeout = 3600000;
		1588	struct pollfd fds [nfd];
		1589	// actual code will need to loop here and realloc etc.
		1590	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1591
		1592	/* the callback is illegal, but won't be called as we stop during check */
		1593	ev_timer_init (&tw, 0, timeout * 1e-3);
		1594	ev_timer_start (loop, &tw);
		1595
		1596	// create one ev_io per pollfd
		1597	for (int i = 0; i < nfd; ++i)
		1598	{
		1599	ev_io_init (iow + i, io_cb, fds [i].fd,
		1600	((fds [i].events & POLLIN ? EV_READ : 0)
		1601	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1602
		1603	fds [i].revents = 0;
		1604	ev_io_start (loop, iow + i);
		1605	}
		1606	}
		1607
		1608	// stop all watchers after blocking
		1609	static void
		1610	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1611	{
		1612	ev_timer_stop (loop, &tw);
		1613
		1614	for (int i = 0; i < nfd; ++i)
		1615	{
		1616	// set the relevant poll flags
		1617	// could also call adns_processreadable etc. here
		1618	struct pollfd *fd = fds + i;
		1619	int revents = ev_clear_pending (iow + i);
		1620	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1621	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1622
		1623	// now stop the watcher
		1624	ev_io_stop (loop, iow + i);
		1625	}
		1626
		1627	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1628	}
		1629
		1630	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1631	in the prepare watcher and would dispose of the check watcher.
		1632
		1633	Method 3: If the module to be embedded supports explicit event
		1634	notification (adns does), you can also make use of the actual watcher
		1635	callbacks, and only destroy/create the watchers in the prepare watcher.
		1636
		1637	static void
		1638	timer_cb (EV_P_ ev_timer *w, int revents)
		1639	{
		1640	adns_state ads = (adns_state)w->data;
		1641	update_now (EV_A);
		1642
		1643	adns_processtimeouts (ads, &tv_now);
		1644	}
		1645
		1646	static void
		1647	io_cb (EV_P_ ev_io *w, int revents)
		1648	{
		1649	adns_state ads = (adns_state)w->data;
		1650	update_now (EV_A);
		1651
		1652	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1653	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1654	}
		1655
		1656	// do not ever call adns_afterpoll
		1657
		1658	Method 4: Do not use a prepare or check watcher because the module you
		1659	want to embed is too inflexible to support it. Instead, youc na override
		1660	their poll function. The drawback with this solution is that the main
		1661	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1662	this.
		1663
		1664	static gint
		1665	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1666	{
		1667	int got_events = 0;
		1668
		1669	for (n = 0; n < nfds; ++n)
		1670	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1671
		1672	if (timeout >= 0)
		1673	// create/start timer
		1674
		1675	// poll
		1676	ev_loop (EV_A_ 0);
		1677
		1678	// stop timer again
		1679	if (timeout >= 0)
		1680	ev_timer_stop (EV_A_ &to);
		1681
		1682	// stop io watchers again - their callbacks should have set
		1683	for (n = 0; n < nfds; ++n)
		1684	ev_io_stop (EV_A_ iow [n]);
		1685
		1686	return got_events;
		1687	}
		1688
		1689
		1690	=head2 C<ev_embed> - when one backend isn't enough...
		1691
		1692	This is a rather advanced watcher type that lets you embed one event loop
		1693	into another (currently only C<ev_io> events are supported in the embedded
		1694	loop, other types of watchers might be handled in a delayed or incorrect
		1695	fashion and must not be used).
		1696
		1697	There are primarily two reasons you would want that: work around bugs and
		1698	prioritise I/O.
		1699
		1700	As an example for a bug workaround, the kqueue backend might only support
		1701	sockets on some platform, so it is unusable as generic backend, but you
		1702	still want to make use of it because you have many sockets and it scales
		1703	so nicely. In this case, you would create a kqueue-based loop and embed it
		1704	into your default loop (which might use e.g. poll). Overall operation will
		1705	be a bit slower because first libev has to poll and then call kevent, but
		1706	at least you can use both at what they are best.
		1707
		1708	As for prioritising I/O: rarely you have the case where some fds have
		1709	to be watched and handled very quickly (with low latency), and even
		1710	priorities and idle watchers might have too much overhead. In this case
		1711	you would put all the high priority stuff in one loop and all the rest in
		1712	a second one, and embed the second one in the first.
		1713
		1714	As long as the watcher is active, the callback will be invoked every time
		1715	there might be events pending in the embedded loop. The callback must then
		1716	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1717	their callbacks (you could also start an idle watcher to give the embedded
		1718	loop strictly lower priority for example). You can also set the callback
		1719	to C<0>, in which case the embed watcher will automatically execute the
		1720	embedded loop sweep.
		1721
		1722	As long as the watcher is started it will automatically handle events. The
		1723	callback will be invoked whenever some events have been handled. You can
		1724	set the callback to C<0> to avoid having to specify one if you are not
		1725	interested in that.
		1726
		1727	Also, there have not currently been made special provisions for forking:
		1728	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1729	but you will also have to stop and restart any C<ev_embed> watchers
		1730	yourself.
		1731
		1732	Unfortunately, not all backends are embeddable, only the ones returned by
		1733	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1734	portable one.
		1735
		1736	So when you want to use this feature you will always have to be prepared
		1737	that you cannot get an embeddable loop. The recommended way to get around
		1738	this is to have a separate variables for your embeddable loop, try to
		1739	create it, and if that fails, use the normal loop for everything:
		1740
		1741	struct ev_loop *loop_hi = ev_default_init (0);
		1742	struct ev_loop *loop_lo = 0;
		1743	struct ev_embed embed;
		1744
		1745	// see if there is a chance of getting one that works
		1746	// (remember that a flags value of 0 means autodetection)
		1747	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1748	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1749	: 0;
		1750
		1751	// if we got one, then embed it, otherwise default to loop_hi
		1752	if (loop_lo)
		1753	{
		1754	ev_embed_init (&embed, 0, loop_lo);
		1755	ev_embed_start (loop_hi, &embed);
		1756	}
		1757	else
		1758	loop_lo = loop_hi;
		1759
		1760	=head3 Watcher-Specific Functions and Data Members
		1761
		1762	=over 4
		1763
		1764	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1765
		1766	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1767
		1768	Configures the watcher to embed the given loop, which must be
		1769	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1770	invoked automatically, otherwise it is the responsibility of the callback
		1771	to invoke it (it will continue to be called until the sweep has been done,
		1772	if you do not want thta, you need to temporarily stop the embed watcher).
		1773
		1774	=item ev_embed_sweep (loop, ev_embed *)
		1775
		1776	Make a single, non-blocking sweep over the embedded loop. This works
		1777	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1778	apropriate way for embedded loops.
		1779
		1780	=item struct ev_loop *loop [read-only]
		1781
		1782	The embedded event loop.
		1783
		1784	=back
		1785
		1786
		1787	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1788
		1789	Fork watchers are called when a C<fork ()> was detected (usually because
		1790	whoever is a good citizen cared to tell libev about it by calling
		1791	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1792	event loop blocks next and before C<ev_check> watchers are being called,
		1793	and only in the child after the fork. If whoever good citizen calling
		1794	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1795	handlers will be invoked, too, of course.
		1796
		1797	=over 4
		1798
		1799	=item ev_fork_init (ev_signal *, callback)
		1800
		1801	Initialises and configures the fork watcher - it has no parameters of any
		1802	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1803	believe me.
		1804
		1805	=back
		1806
		1807
712	=head1 OTHER FUNCTIONS	1808	=head1 OTHER FUNCTIONS
713		1809
714	There are some other functions of possible interest. Described. Here. Now.	1810	There are some other functions of possible interest. Described. Here. Now.
715		1811
716	=over 4	1812	=over 4
…		…
718	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1814	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
719		1815
720	This function combines a simple timer and an I/O watcher, calls your	1816	This function combines a simple timer and an I/O watcher, calls your
721	callback on whichever event happens first and automatically stop both	1817	callback on whichever event happens first and automatically stop both
722	watchers. This is useful if you want to wait for a single event on an fd	1818	watchers. This is useful if you want to wait for a single event on an fd
723	or timeout without havign to allocate/configure/start/stop/free one or	1819	or timeout without having to allocate/configure/start/stop/free one or
724	more watchers yourself.	1820	more watchers yourself.
725		1821
726	If C<fd> is less than 0, then no I/O watcher will be started and events	1822	If C<fd> is less than 0, then no I/O watcher will be started and events
727	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	1823	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
728	C<events> set will be craeted and started.	1824	C<events> set will be craeted and started.
…		…
731	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	1827	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
732	repeat = 0) will be started. While C<0> is a valid timeout, it is of	1828	repeat = 0) will be started. While C<0> is a valid timeout, it is of
733	dubious value.	1829	dubious value.
734		1830
735	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	1831	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
736	passed an events set like normal event callbacks (with a combination of	1832	passed an C<revents> set like normal event callbacks (a combination of
737	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	1833	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
738	value passed to C<ev_once>:	1834	value passed to C<ev_once>:
739		1835
740	static void stdin_ready (int revents, void *arg)	1836	static void stdin_ready (int revents, void *arg)
741	{	1837	{
…		…
745	/* stdin might have data for us, joy! */;	1841	/* stdin might have data for us, joy! */;
746	}	1842	}
747		1843
748	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1844	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
749		1845
750	=item ev_feed_event (loop, watcher, int events)	1846	=item ev_feed_event (ev_loop *, watcher *, int revents)
751		1847
752	Feeds the given event set into the event loop, as if the specified event	1848	Feeds the given event set into the event loop, as if the specified event
753	had happened for the specified watcher (which must be a pointer to an	1849	had happened for the specified watcher (which must be a pointer to an
754	initialised but not necessarily started event watcher).	1850	initialised but not necessarily started event watcher).
755		1851
756	=item ev_feed_fd_event (loop, int fd, int revents)	1852	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
757		1853
758	Feed an event on the given fd, as if a file descriptor backend detected	1854	Feed an event on the given fd, as if a file descriptor backend detected
759	the given events it.	1855	the given events it.
760		1856
761	=item ev_feed_signal_event (loop, int signum)	1857	=item ev_feed_signal_event (ev_loop *loop, int signum)
762		1858
763	Feed an event as if the given signal occured (loop must be the default loop!).	1859	Feed an event as if the given signal occured (C<loop> must be the default
		1860	loop!).
764		1861
765	=back	1862	=back
766		1863
		1864
		1865	=head1 LIBEVENT EMULATION
		1866
		1867	Libev offers a compatibility emulation layer for libevent. It cannot
		1868	emulate the internals of libevent, so here are some usage hints:
		1869
		1870	=over 4
		1871
		1872	=item * Use it by including <event.h>, as usual.
		1873
		1874	=item * The following members are fully supported: ev_base, ev_callback,
		1875	ev_arg, ev_fd, ev_res, ev_events.
		1876
		1877	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1878	maintained by libev, it does not work exactly the same way as in libevent (consider
		1879	it a private API).
		1880
		1881	=item * Priorities are not currently supported. Initialising priorities
		1882	will fail and all watchers will have the same priority, even though there
		1883	is an ev_pri field.
		1884
		1885	=item * Other members are not supported.
		1886
		1887	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1888	to use the libev header file and library.
		1889
		1890	=back
		1891
		1892	=head1 C++ SUPPORT
		1893
		1894	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1895	you to use some convinience methods to start/stop watchers and also change
		1896	the callback model to a model using method callbacks on objects.
		1897
		1898	To use it,
		1899
		1900	#include <ev++.h>
		1901
		1902	This automatically includes F<ev.h> and puts all of its definitions (many
		1903	of them macros) into the global namespace. All C++ specific things are
		1904	put into the C<ev> namespace. It should support all the same embedding
		1905	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		1906
		1907	Care has been taken to keep the overhead low. The only data member the C++
		1908	classes add (compared to plain C-style watchers) is the event loop pointer
		1909	that the watcher is associated with (or no additional members at all if
		1910	you disable C<EV_MULTIPLICITY> when embedding libev).
		1911
		1912	Currently, functions, and static and non-static member functions can be
		1913	used as callbacks. Other types should be easy to add as long as they only
		1914	need one additional pointer for context. If you need support for other
		1915	types of functors please contact the author (preferably after implementing
		1916	it).
		1917
		1918	Here is a list of things available in the C<ev> namespace:
		1919
		1920	=over 4
		1921
		1922	=item C<ev::READ>, C<ev::WRITE> etc.
		1923
		1924	These are just enum values with the same values as the C<EV_READ> etc.
		1925	macros from F<ev.h>.
		1926
		1927	=item C<ev::tstamp>, C<ev::now>
		1928
		1929	Aliases to the same types/functions as with the C<ev_> prefix.
		1930
		1931	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1932
		1933	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1934	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1935	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1936	defines by many implementations.
		1937
		1938	All of those classes have these methods:
		1939
		1940	=over 4
		1941
		1942	=item ev::TYPE::TYPE ()
		1943
		1944	=item ev::TYPE::TYPE (struct ev_loop *)
		1945
		1946	=item ev::TYPE::~TYPE
		1947
		1948	The constructor (optionally) takes an event loop to associate the watcher
		1949	with. If it is omitted, it will use C<EV_DEFAULT>.
		1950
		1951	The constructor calls C<ev_init> for you, which means you have to call the
		1952	C<set> method before starting it.
		1953
		1954	It will not set a callback, however: You have to call the templated C<set>
		1955	method to set a callback before you can start the watcher.
		1956
		1957	(The reason why you have to use a method is a limitation in C++ which does
		1958	not allow explicit template arguments for constructors).
		1959
		1960	The destructor automatically stops the watcher if it is active.
		1961
		1962	=item w->set<class, &class::method> (object *)
		1963
		1964	This method sets the callback method to call. The method has to have a
		1965	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1966	first argument and the C<revents> as second. The object must be given as
		1967	parameter and is stored in the C<data> member of the watcher.
		1968
		1969	This method synthesizes efficient thunking code to call your method from
		1970	the C callback that libev requires. If your compiler can inline your
		1971	callback (i.e. it is visible to it at the place of the C<set> call and
		1972	your compiler is good :), then the method will be fully inlined into the
		1973	thunking function, making it as fast as a direct C callback.
		1974
		1975	Example: simple class declaration and watcher initialisation
		1976
		1977	struct myclass
		1978	{
		1979	void io_cb (ev::io &w, int revents) { }
		1980	}
		1981
		1982	myclass obj;
		1983	ev::io iow;
		1984	iow.set <myclass, &myclass::io_cb> (&obj);
		1985
		1986	=item w->set<function> (void *data = 0)
		1987
		1988	Also sets a callback, but uses a static method or plain function as
		1989	callback. The optional C<data> argument will be stored in the watcher's
		1990	C<data> member and is free for you to use.
		1991
		1992	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1993
		1994	See the method-C<set> above for more details.
		1995
		1996	Example:
		1997
		1998	static void io_cb (ev::io &w, int revents) { }
		1999	iow.set <io_cb> ();
		2000
		2001	=item w->set (struct ev_loop *)
		2002
		2003	Associates a different C<struct ev_loop> with this watcher. You can only
		2004	do this when the watcher is inactive (and not pending either).
		2005
		2006	=item w->set ([args])
		2007
		2008	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2009	called at least once. Unlike the C counterpart, an active watcher gets
		2010	automatically stopped and restarted when reconfiguring it with this
		2011	method.
		2012
		2013	=item w->start ()
		2014
		2015	Starts the watcher. Note that there is no C<loop> argument, as the
		2016	constructor already stores the event loop.
		2017
		2018	=item w->stop ()
		2019
		2020	Stops the watcher if it is active. Again, no C<loop> argument.
		2021
		2022	=item w->again () C<ev::timer>, C<ev::periodic> only
		2023
		2024	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2025	C<ev_TYPE_again> function.
		2026
		2027	=item w->sweep () C<ev::embed> only
		2028
		2029	Invokes C<ev_embed_sweep>.
		2030
		2031	=item w->update () C<ev::stat> only
		2032
		2033	Invokes C<ev_stat_stat>.
		2034
		2035	=back
		2036
		2037	=back
		2038
		2039	Example: Define a class with an IO and idle watcher, start one of them in
		2040	the constructor.
		2041
		2042	class myclass
		2043	{
		2044	ev_io io; void io_cb (ev::io &w, int revents);
		2045	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2046
		2047	myclass ();
		2048	}
		2049
		2050	myclass::myclass (int fd)
		2051	{
		2052	io .set <myclass, &myclass::io_cb > (this);
		2053	idle.set <myclass, &myclass::idle_cb> (this);
		2054
		2055	io.start (fd, ev::READ);
		2056	}
		2057
		2058
		2059	=head1 MACRO MAGIC
		2060
		2061	Libev can be compiled with a variety of options, the most fundemantal is
		2062	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
		2063	callbacks have an initial C<struct ev_loop *> argument.
		2064
		2065	To make it easier to write programs that cope with either variant, the
		2066	following macros are defined:
		2067
		2068	=over 4
		2069
		2070	=item C<EV_A>, C<EV_A_>
		2071
		2072	This provides the loop I<argument> for functions, if one is required ("ev
		2073	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2074	C<EV_A_> is used when other arguments are following. Example:
		2075
		2076	ev_unref (EV_A);
		2077	ev_timer_add (EV_A_ watcher);
		2078	ev_loop (EV_A_ 0);
		2079
		2080	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2081	which is often provided by the following macro.
		2082
		2083	=item C<EV_P>, C<EV_P_>
		2084
		2085	This provides the loop I<parameter> for functions, if one is required ("ev
		2086	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2087	C<EV_P_> is used when other parameters are following. Example:
		2088
		2089	// this is how ev_unref is being declared
		2090	static void ev_unref (EV_P);
		2091
		2092	// this is how you can declare your typical callback
		2093	static void cb (EV_P_ ev_timer *w, int revents)
		2094
		2095	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2096	suitable for use with C<EV_A>.
		2097
		2098	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2099
		2100	Similar to the other two macros, this gives you the value of the default
		2101	loop, if multiple loops are supported ("ev loop default").
		2102
		2103	=back
		2104
		2105	Example: Declare and initialise a check watcher, utilising the above
		2106	macros so it will work regardless of whether multiple loops are supported
		2107	or not.
		2108
		2109	static void
		2110	check_cb (EV_P_ ev_timer *w, int revents)
		2111	{
		2112	ev_check_stop (EV_A_ w);
		2113	}
		2114
		2115	ev_check check;
		2116	ev_check_init (&check, check_cb);
		2117	ev_check_start (EV_DEFAULT_ &check);
		2118	ev_loop (EV_DEFAULT_ 0);
		2119
		2120	=head1 EMBEDDING
		2121
		2122	Libev can (and often is) directly embedded into host
		2123	applications. Examples of applications that embed it include the Deliantra
		2124	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2125	and rxvt-unicode.
		2126
		2127	The goal is to enable you to just copy the neecssary files into your
		2128	source directory without having to change even a single line in them, so
		2129	you can easily upgrade by simply copying (or having a checked-out copy of
		2130	libev somewhere in your source tree).
		2131
		2132	=head2 FILESETS
		2133
		2134	Depending on what features you need you need to include one or more sets of files
		2135	in your app.
		2136
		2137	=head3 CORE EVENT LOOP
		2138
		2139	To include only the libev core (all the C<ev_*> functions), with manual
		2140	configuration (no autoconf):
		2141
		2142	#define EV_STANDALONE 1
		2143	#include "ev.c"
		2144
		2145	This will automatically include F<ev.h>, too, and should be done in a
		2146	single C source file only to provide the function implementations. To use
		2147	it, do the same for F<ev.h> in all files wishing to use this API (best
		2148	done by writing a wrapper around F<ev.h> that you can include instead and
		2149	where you can put other configuration options):
		2150
		2151	#define EV_STANDALONE 1
		2152	#include "ev.h"
		2153
		2154	Both header files and implementation files can be compiled with a C++
		2155	compiler (at least, thats a stated goal, and breakage will be treated
		2156	as a bug).
		2157
		2158	You need the following files in your source tree, or in a directory
		2159	in your include path (e.g. in libev/ when using -Ilibev):
		2160
		2161	ev.h
		2162	ev.c
		2163	ev_vars.h
		2164	ev_wrap.h
		2165
		2166	ev_win32.c required on win32 platforms only
		2167
		2168	ev_select.c only when select backend is enabled (which is enabled by default)
		2169	ev_poll.c only when poll backend is enabled (disabled by default)
		2170	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2171	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2172	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2173
		2174	F<ev.c> includes the backend files directly when enabled, so you only need
		2175	to compile this single file.
		2176
		2177	=head3 LIBEVENT COMPATIBILITY API
		2178
		2179	To include the libevent compatibility API, also include:
		2180
		2181	#include "event.c"
		2182
		2183	in the file including F<ev.c>, and:
		2184
		2185	#include "event.h"
		2186
		2187	in the files that want to use the libevent API. This also includes F<ev.h>.
		2188
		2189	You need the following additional files for this:
		2190
		2191	event.h
		2192	event.c
		2193
		2194	=head3 AUTOCONF SUPPORT
		2195
		2196	Instead of using C<EV_STANDALONE=1> and providing your config in
		2197	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2198	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2199	include F<config.h> and configure itself accordingly.
		2200
		2201	For this of course you need the m4 file:
		2202
		2203	libev.m4
		2204
		2205	=head2 PREPROCESSOR SYMBOLS/MACROS
		2206
		2207	Libev can be configured via a variety of preprocessor symbols you have to define
		2208	before including any of its files. The default is not to build for multiplicity
		2209	and only include the select backend.
		2210
		2211	=over 4
		2212
		2213	=item EV_STANDALONE
		2214
		2215	Must always be C<1> if you do not use autoconf configuration, which
		2216	keeps libev from including F<config.h>, and it also defines dummy
		2217	implementations for some libevent functions (such as logging, which is not
		2218	supported). It will also not define any of the structs usually found in
		2219	F<event.h> that are not directly supported by the libev core alone.
		2220
		2221	=item EV_USE_MONOTONIC
		2222
		2223	If defined to be C<1>, libev will try to detect the availability of the
		2224	monotonic clock option at both compiletime and runtime. Otherwise no use
		2225	of the monotonic clock option will be attempted. If you enable this, you
		2226	usually have to link against librt or something similar. Enabling it when
		2227	the functionality isn't available is safe, though, althoguh you have
		2228	to make sure you link against any libraries where the C<clock_gettime>
		2229	function is hiding in (often F<-lrt>).
		2230
		2231	=item EV_USE_REALTIME
		2232
		2233	If defined to be C<1>, libev will try to detect the availability of the
		2234	realtime clock option at compiletime (and assume its availability at
		2235	runtime if successful). Otherwise no use of the realtime clock option will
		2236	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2237	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		2238	in the description of C<EV_USE_MONOTONIC>, though.
		2239
		2240	=item EV_USE_SELECT
		2241
		2242	If undefined or defined to be C<1>, libev will compile in support for the
		2243	C<select>(2) backend. No attempt at autodetection will be done: if no
		2244	other method takes over, select will be it. Otherwise the select backend
		2245	will not be compiled in.
		2246
		2247	=item EV_SELECT_USE_FD_SET
		2248
		2249	If defined to C<1>, then the select backend will use the system C<fd_set>
		2250	structure. This is useful if libev doesn't compile due to a missing
		2251	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2252	exotic systems. This usually limits the range of file descriptors to some
		2253	low limit such as 1024 or might have other limitations (winsocket only
		2254	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2255	influence the size of the C<fd_set> used.
		2256
		2257	=item EV_SELECT_IS_WINSOCKET
		2258
		2259	When defined to C<1>, the select backend will assume that
		2260	select/socket/connect etc. don't understand file descriptors but
		2261	wants osf handles on win32 (this is the case when the select to
		2262	be used is the winsock select). This means that it will call
		2263	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2264	it is assumed that all these functions actually work on fds, even
		2265	on win32. Should not be defined on non-win32 platforms.
		2266
		2267	=item EV_USE_POLL
		2268
		2269	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2270	backend. Otherwise it will be enabled on non-win32 platforms. It
		2271	takes precedence over select.
		2272
		2273	=item EV_USE_EPOLL
		2274
		2275	If defined to be C<1>, libev will compile in support for the Linux
		2276	C<epoll>(7) backend. Its availability will be detected at runtime,
		2277	otherwise another method will be used as fallback. This is the
		2278	preferred backend for GNU/Linux systems.
		2279
		2280	=item EV_USE_KQUEUE
		2281
		2282	If defined to be C<1>, libev will compile in support for the BSD style
		2283	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2284	otherwise another method will be used as fallback. This is the preferred
		2285	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2286	supports some types of fds correctly (the only platform we found that
		2287	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2288	not be used unless explicitly requested. The best way to use it is to find
		2289	out whether kqueue supports your type of fd properly and use an embedded
		2290	kqueue loop.
		2291
		2292	=item EV_USE_PORT
		2293
		2294	If defined to be C<1>, libev will compile in support for the Solaris
		2295	10 port style backend. Its availability will be detected at runtime,
		2296	otherwise another method will be used as fallback. This is the preferred
		2297	backend for Solaris 10 systems.
		2298
		2299	=item EV_USE_DEVPOLL
		2300
		2301	reserved for future expansion, works like the USE symbols above.
		2302
		2303	=item EV_USE_INOTIFY
		2304
		2305	If defined to be C<1>, libev will compile in support for the Linux inotify
		2306	interface to speed up C<ev_stat> watchers. Its actual availability will
		2307	be detected at runtime.
		2308
		2309	=item EV_H
		2310
		2311	The name of the F<ev.h> header file used to include it. The default if
		2312	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2313	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2314
		2315	=item EV_CONFIG_H
		2316
		2317	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2318	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2319	C<EV_H>, above.
		2320
		2321	=item EV_EVENT_H
		2322
		2323	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2324	of how the F<event.h> header can be found.
		2325
		2326	=item EV_PROTOTYPES
		2327
		2328	If defined to be C<0>, then F<ev.h> will not define any function
		2329	prototypes, but still define all the structs and other symbols. This is
		2330	occasionally useful if you want to provide your own wrapper functions
		2331	around libev functions.
		2332
		2333	=item EV_MULTIPLICITY
		2334
		2335	If undefined or defined to C<1>, then all event-loop-specific functions
		2336	will have the C<struct ev_loop *> as first argument, and you can create
		2337	additional independent event loops. Otherwise there will be no support
		2338	for multiple event loops and there is no first event loop pointer
		2339	argument. Instead, all functions act on the single default loop.
		2340
		2341	=item EV_MINPRI
		2342
		2343	=item EV_MAXPRI
		2344
		2345	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2346	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2347	provide for more priorities by overriding those symbols (usually defined
		2348	to be C<-2> and C<2>, respectively).
		2349
		2350	When doing priority-based operations, libev usually has to linearly search
		2351	all the priorities, so having many of them (hundreds) uses a lot of space
		2352	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2353	fine.
		2354
		2355	If your embedding app does not need any priorities, defining these both to
		2356	C<0> will save some memory and cpu.
		2357
		2358	=item EV_PERIODIC_ENABLE
		2359
		2360	If undefined or defined to be C<1>, then periodic timers are supported. If
		2361	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2362	code.
		2363
		2364	=item EV_IDLE_ENABLE
		2365
		2366	If undefined or defined to be C<1>, then idle watchers are supported. If
		2367	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2368	code.
		2369
		2370	=item EV_EMBED_ENABLE
		2371
		2372	If undefined or defined to be C<1>, then embed watchers are supported. If
		2373	defined to be C<0>, then they are not.
		2374
		2375	=item EV_STAT_ENABLE
		2376
		2377	If undefined or defined to be C<1>, then stat watchers are supported. If
		2378	defined to be C<0>, then they are not.
		2379
		2380	=item EV_FORK_ENABLE
		2381
		2382	If undefined or defined to be C<1>, then fork watchers are supported. If
		2383	defined to be C<0>, then they are not.
		2384
		2385	=item EV_MINIMAL
		2386
		2387	If you need to shave off some kilobytes of code at the expense of some
		2388	speed, define this symbol to C<1>. Currently only used for gcc to override
		2389	some inlining decisions, saves roughly 30% codesize of amd64.
		2390
		2391	=item EV_PID_HASHSIZE
		2392
		2393	C<ev_child> watchers use a small hash table to distribute workload by
		2394	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2395	than enough. If you need to manage thousands of children you might want to
		2396	increase this value (I<must> be a power of two).
		2397
		2398	=item EV_INOTIFY_HASHSIZE
		2399
		2400	C<ev_staz> watchers use a small hash table to distribute workload by
		2401	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2402	usually more than enough. If you need to manage thousands of C<ev_stat>
		2403	watchers you might want to increase this value (I<must> be a power of
		2404	two).
		2405
		2406	=item EV_COMMON
		2407
		2408	By default, all watchers have a C<void *data> member. By redefining
		2409	this macro to a something else you can include more and other types of
		2410	members. You have to define it each time you include one of the files,
		2411	though, and it must be identical each time.
		2412
		2413	For example, the perl EV module uses something like this:
		2414
		2415	#define EV_COMMON \
		2416	SV *self; /* contains this struct */ \
		2417	SV *cb_sv, *fh /* note no trailing ";" */
		2418
		2419	=item EV_CB_DECLARE (type)
		2420
		2421	=item EV_CB_INVOKE (watcher, revents)
		2422
		2423	=item ev_set_cb (ev, cb)
		2424
		2425	Can be used to change the callback member declaration in each watcher,
		2426	and the way callbacks are invoked and set. Must expand to a struct member
		2427	definition and a statement, respectively. See the F<ev.v> header file for
		2428	their default definitions. One possible use for overriding these is to
		2429	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2430	method calls instead of plain function calls in C++.
		2431
		2432	=head2 EXAMPLES
		2433
		2434	For a real-world example of a program the includes libev
		2435	verbatim, you can have a look at the EV perl module
		2436	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2437	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2438	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2439	will be compiled. It is pretty complex because it provides its own header
		2440	file.
		2441
		2442	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2443	that everybody includes and which overrides some configure choices:
		2444
		2445	#define EV_MINIMAL 1
		2446	#define EV_USE_POLL 0
		2447	#define EV_MULTIPLICITY 0
		2448	#define EV_PERIODIC_ENABLE 0
		2449	#define EV_STAT_ENABLE 0
		2450	#define EV_FORK_ENABLE 0
		2451	#define EV_CONFIG_H <config.h>
		2452	#define EV_MINPRI 0
		2453	#define EV_MAXPRI 0
		2454
		2455	#include "ev++.h"
		2456
		2457	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2458
		2459	#include "ev_cpp.h"
		2460	#include "ev.c"
		2461
		2462
		2463	=head1 COMPLEXITIES
		2464
		2465	In this section the complexities of (many of) the algorithms used inside
		2466	libev will be explained. For complexity discussions about backends see the
		2467	documentation for C<ev_default_init>.
		2468
		2469	All of the following are about amortised time: If an array needs to be
		2470	extended, libev needs to realloc and move the whole array, but this
		2471	happens asymptotically never with higher number of elements, so O(1) might
		2472	mean it might do a lengthy realloc operation in rare cases, but on average
		2473	it is much faster and asymptotically approaches constant time.
		2474
		2475	=over 4
		2476
		2477	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2478
		2479	This means that, when you have a watcher that triggers in one hour and
		2480	there are 100 watchers that would trigger before that then inserting will
		2481	have to skip those 100 watchers.
		2482
		2483	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2484
		2485	That means that for changing a timer costs less than removing/adding them
		2486	as only the relative motion in the event queue has to be paid for.
		2487
		2488	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2489
		2490	These just add the watcher into an array or at the head of a list.
		2491	=item Stopping check/prepare/idle watchers: O(1)
		2492
		2493	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2494
		2495	These watchers are stored in lists then need to be walked to find the
		2496	correct watcher to remove. The lists are usually short (you don't usually
		2497	have many watchers waiting for the same fd or signal).
		2498
		2499	=item Finding the next timer per loop iteration: O(1)
		2500
		2501	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2502
		2503	A change means an I/O watcher gets started or stopped, which requires
		2504	libev to recalculate its status (and possibly tell the kernel).
		2505
		2506	=item Activating one watcher: O(1)
		2507
		2508	=item Priority handling: O(number_of_priorities)
		2509
		2510	Priorities are implemented by allocating some space for each
		2511	priority. When doing priority-based operations, libev usually has to
		2512	linearly search all the priorities.
		2513
		2514	=back
		2515
		2516
767	=head1 AUTHOR	2517	=head1 AUTHOR
768		2518
769	Marc Lehmann <libev@schmorp.de>.	2519	Marc Lehmann <libev@schmorp.de>.
770		2520

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